1. Field of the Invention
The invention relates to clutches, and particularly, to clutches which are operated automatically by centrifugal force at a predetermined speed of rotation so as to connect a driving member or load. More particularly, the invention relates to an improved rotor assembly of a centrifugal clutch in which a pair of clutch shoes are pivotally mounted on a novel integral hub collar and pivot pin assembly.
2. Description of the Prior Art
There are numerous types and arrangements of centrifugal clutch constructions in which pivotally mounted clutch shoes are retained in retracted position by springs or other retaining means until sufficient centrifugal force acts on the shoes during rotation of the clutch rotor to overcome the retaining force of the springs. The clutch shoes then pivot and swing outwardly to drivingly engage a concentrically located clutch housing or drum.
Many of these clutch constructions have a pair of arcuate-shaped clutch shoes which are pivotally mounted on a backing plate or drive flange and arranged in an end-to-end relationship with respect to each other. The backing plate or drive flange is fixed to a drive shaft or hub for rotation with the drive shaft. These clutch shoes have various spring arrangements for biasing the shoes toward retracted position, which spring-retaining tensions are overcome by centrifugal force acting on the shoes, whereupon the clutch shoes pivot outwardly and engage the driven member.
There are many types of such centrifugal clutches which have proven satisfactory for their intended purpose. Most of these known clutches use a simple beam-type mounting arrangement for the clutch shoes, wherein a pivot pin is supported on both ends by a pair of backing plates or the like. The pins extend through a circular opening formed in and adjacent to one end of the clutch shoes for pivotally mounting the shoes. Other types of clutches use a cantilever-type mounting arrangement in which the pivot pin is supported at only one end on the backing plate. In both types of constructions, the pin projects through a circular opening in the clutch shoe. Various bushing assemblies may be telescopically mounted on the pivot pins and located within the shoe mounting openings to provide various pivot arrangements.
These clutch constructions have the disadvantage of limiting the outside diameter of the drive shaft with respect to the over-all dimensions of the clutch shoe and clutch diameter, since considerable metal mass is required for the rotor hub and clutch to provide the pivotal mounting of the clutch shoe on the rotor hub or backing plates. These constructions also require the clutch shoes to be spaced farther outward from the axis of the clutch, thereby increasing the over-all diameter of the clutch due to the extra metal required adjacent the inner arcuate edge of the shoes to form the full circular pivot pin opening with sufficient surrounding metal thickness to withstand the repeated shocks and stresses which are exerted on the clutch shoe during engagement with driven clutch member.
Other clutch constructions have clutch shoes which are mounted on pins which extend outwardly from a backing plate in which the shoes are not captured by the pins but have a pivotal sliding movement with respect thereto, as shown in U.S. Pat. Nos. 1,873,561 and 3,026,980. This type of clutch provides different operating characteristics than those clutches in which the shoes are captured by their pivot pins, since the clutch shoes move outwardly and away from the support pin upon engaging the driven housing.
These various clutch constructions also require additional components, such as the backing plate or plates and separate pins, which must be manufactured and mounted thereon by various manufacturing methods, all of which increase the cost of the clutch, and in certain situations, present maintenance problems.
Another pertinent prior art clutch is shown in British Pat. No. 933,615 in which a pair of clutch shoes are movably mounted on cylindrical enlargements formed on the outer ends of a pair of arms which extend outwardly from the hub. This construction defeats one of the main purposes and advantages of my clutch construction, i.e., the location of the clutch shoe pivot points as close to the pivot center of the rotor as possible. The large stresses which would be created in the arms of this type clutch would require greater metal thickness to withstand such stresses, and more importantly, would increase the over-all diameter of the clutch.
Thus, the need has existed for a centrifugal clutch construction of the type in which the clutch shoes are captured by their pivot pins, preventing movement of the shoe end away from the pin without requiring the heretofore relatively large metal masses to form the pivot pin mounting opening in the clutch shoe, and also a clutch construction which enables a maximum outside diameter drive shaft to be used without increasing the over-all diameter of the clutch while still obtaining the same torque characteristics as possible with those clutches which are limited to relatively smaller diameter drive shafts.
There is no known centrifugal clutch construction of which I am aware which provides pivotally mounting the clutch shoes on an integral hub collar and pivot pin arrangement by use of a discontinuous pivot pin opening formed in each of the clutch shoes which captures the clutch shoes on their pivotal mounting pins, in which the imaginary circumferences of the outer surface of each of the mounting pins lies in an overlapping or at least an abutting relationship with the imaginary circumference of the outer surface of the hub collar, which enables a maximum outside diameter drive shaft to be used with the same size clutch shoe heretofore used to achieve the same operating torque characteristics.